Hey everyone! Long time, no blog. Hope everyone’s been enjoying their tea in the meantime – I know I have! I took a trip up to Setting Sun Tea Hut in Vermont, which has beautiful tea, an awesome experience, and great well water for tea – they don’t even have to filter it. There, we had tea with tetsubins, clay kettles (chaozhou and novak), and copper kettles. The differences in each were striking – I had never tried a tetsubin before. I am sure there is a reaction going on in there on the iron-water interface.
In the above reaction, the iron from the kettle binds with the water and releases hydrogen ions. Interestingly, a similar thing happens in a Brita filter, the most popular water filter around.
I’ve been familiar with them for a long time, but only recently did I understand what a Brita filter does. If you have a TDS meter, you may notice that water run through a Brita has around 20% lower TDS reading, and has a more acidic pH. They curiously don’t advertise these two features – probably because “alkaline water” is believed to be better than acidic. But why and how does it do this to the water?
In addition to activated carbon, which improves the water’s taste, Britas contain ion exchange resin pellets. In this case, these are beads that specifically accept a calcium ion (Ca2+) and give off hydrogen ions (2H+). The result of this is twofold. First, the hardness of the water is reduced, due to reduced calcium. Second, the alkalinity of the water is also reduced, because (and this is what I just figured out) the acidic hydrogen ions are neutralized by the HCO3- buffer forming H2CO3, or carbonic acid.
I used to think this was a very mild and subtle change – after all, TDS only goes down 20% on average. But recently, I took very hard, 500 TDS spring water that scales aggressively when boiled, ran it through the Brita, and boiled it. And what did I find? No scale at all. I was shocked! This means that almost all the temporary hardness (calcium-bicarbonate) is taken out. The resulting tea was way different. With the unfiltered 500 TDS water, tea is thick and muted. After the Brita, the water measured only 220 TDS, and the tea was hollow and forward.
This is when I realized that Brita filters radically alter the mineral profile of water. They cause already forward waters to be more forward and hollow out/brighten up, and cause less-present waters to become thinner and milder, but also brighter. Now, don’t get me wrong, they can still make good tea – in fact, I had a great session with an older raw puer last week with Brita-filtered NYC (Brooklyn) tap water. However, it’s definitely worth knowing that Britas don’t just make your tea taste better, they radically alter the mineral composition – and not always for the better. It’s worth testing for yourself – what do you like? Brita, or something like a Waterdrop that doesn’t change mineral content at all? Or even a blend? I personally am still alternating between many different options in order to learn more.